respect to the fundamental Component. Itis
expressed as a ratio of total harmonic voltage to
the fundamental voltage and is called total
harmonic distortion (THD). Generally 5% THD
is considered an allowable limit for an
electrically clean supply.
ADVENT OF HARMONIC FILTERS
In order to improve power factor without causing
harmonic amplification, harmonic filters are to
be used. Harmonic filters are suitably modified
capacitors used together with series reactors,
which are specially designed to improve power
factor and suppress harmonic amplification.
These types of hannonic filters are the passive
type and extensively used in place of
conventional power factor correcting in
harmonic rich environments. A passive filter
basically consists of a series circuit of reactors
and capacitors
The figure below illustrates schematically the
description of passive filtering with a harmonic
generator; impedance representing all other loads
a filter and a network.